EP0979931B1

EP0979931B1 - Mounting a cooling nozzele on an engine block

Info

Publication number: EP0979931B1
Application number: EP99202588A
Authority: EP
Inventors: Nikos J. Chimonides; Gary S. Antcliff
Original assignee: Iveco UK Ltd; Cummins Engine Co Ltd; CNH UK Ltd
Current assignee: Iveco UK Ltd; Cummins Ltd; CNH UK Ltd
Priority date: 1998-08-13
Filing date: 1999-08-06
Publication date: 2004-05-12
Anticipated expiration: 2019-08-06
Also published as: GB2340578A; JP4422824B2; GB9817530D0; JP2000064836A; DE69917155T2; US6298810B1; EP0979931A1; DE69917155D1

Description

The present invention relates to the mounting of a cooling nozzle on an engine block in order to direct a nozzle or spray of oil at the underside of a reciprocating piston.
It is known to cool a piston by directing a spray or nozzle of oil at its underside. For this purpose, a nozzle is secured to the engine block by means of a capscrew and communicates through the capscrew with an oil gallery in the engine block. Conventionally, the capscrew passing through a hole in the base or mounting collar of the nozzle serves as the means for correctly positioning and aligning the nozzle in the block but very accurate machining is required both in the drilling and in the tapping of the bore in the engine block on account of the precision with which it is essential to locate the oil nozzle. In this context, it should be noted that the clearance between the crankshaft, the connecting rod and the piston is typically 5 mm, but it can be as little as 3 mm.
From JP 61244820 it is known to mount an oil nozzle on a machined part of a crankcase whereby a bolt tightly passes through the body of the nozzle to engage a threaded bore which intersects an oil gallery. As such, the position of the nozzle is determined by the position of the bolt and hence by the exact location of the thread in the bore. In this arrangement, to ensure 'high precision mounting, high precision machining and threading are required.
The nozzle arrangement shown in FR-A-2.095.745 comprises an oil supply tube to which various nozzles are attached. Although the document claims to be able to orient the nozzle with precision, this is highly doubtful for a number of reasons. First of all, the tube will not present a totally rigid structure and thus may flex, thereby changing the orientation of the attached nozzles. Furthermore, although no details are given about the way the surfaces and bores in the tube for receiving the nozzles are machined, a man skilled in the art will readily realise that machining a tube with accuracy is very difficult. As there furthermore seems to be no interrelation between the threaded bore receiving a bolt and the surface upon which a nozzle rests, misalignment and twisting of a nozzle easily may occur, the more that the mounting collar of the nozzle is quite long, increasing the lever arm by which the bolt presses on the nozzle. Moreover, since the oil supply tube has to be attached to the engine block by additional fixation means, further mounting tolerances have to be added. Finally, since the bolt engages the nozzle along its longitudinal axis, the orientation of the nozzle will be determined by the bolt. As such, the slightest incorrectness in position of the threaded bore receiving the bolt will result in a considerable deviation of the nozzle from its correct position. All this makes it virtually impossible to arrive at the level of accuracy required by the present invention to precisely locate and orient a nozzle relative to the moving parts of an engine.
It is therefore an object of the present invention to provide a mounting of the nozzle on the engine block that can reliably achieve accurate alignment positioning of the oil nozzle without resorting to high precision machining and without having to rely on the position of the bolt fixing the oil nozzle in place.
According to a first aspect of the present invention, there is provided a method of mounting an oil nozzle on an engine block, the oil nozzle comprising an annular mounting collar having a cylindrical outer surface and a tube projecting generally radially from the mounting collar.
The method is characterized in that it comprises the steps of :

drilling a bore in the engine block to intersect an oil gallery in the engine block;
machining a cylindrical recess in the surface of the cylinder block surrounding the mouth of the bore for receiving and locating the mounting collar of the nozzle; the cylindrical recess and the bore being formed at the same time using a suitably shaped drilling tool so as to ensure on the one hand that the recess and the bore are concentric and on the other hand that the machined sealing surface of the recess is normal to the axis of the bore;
tapping a thread in the bore;
placing the mounting collar of the nozzle in the recess;
inserting a capscrew with radial play through the collar into the threaded bore to retain the collar within the recess; the capscrew allowing oil to flow from the oil gallery in the block into the mounting collar of the oil nozzle; and
sealing the collar against the sealing surface of the recess by means of the capscrew.

In the invention, the position of the oil nozzle in the engine block is not determined by the location of the threaded bore and the capscrew but by the engagement of the outer surface of the mounting collar of the nozzle in the recess machined in the surface of the engine block surrounding the threaded bore. As a result, if a misalignment occurs while tapping the screw thread in the bore, resulting in misalignment of the capscrew, this will not affect the correct positioning of the oil nozzle in the engine block.
Aside from the improved accuracy in the positioning of the oil nozzle in the engine block, the invention provides a cost saving in that conventionally the entire surface of the engine block on which the oil nozzles are mounted needs to be machined flat, whereas in the invention only the cylindrical recesses in which the oil nozzles are mounted need to have machined sealing surfaces.
The simultaneous formation of the cylindrical recess and the bore using a suitably shaped drilling tool not only achieves increased cost saving but also ensures that the bore is centred in the cylindrical recess and is normal to the surface against which the mounting collar of the nozzle seals.
It is further preferred to form the capscrew by providing a blank having one or more axially extending oil grooves in its surface and cutting a thread in the blank that is less deep than the grooves. This allows the formation, in a single machining operation, of a capscrew having grooves through which oil can flow from the gallery in the engine block into the mounting collar of the oil nozzle.
In addition to locating the centre of the mounting collar of the nozzle accurately in relation to the engine block, it is necessary to achieve an accurate orientation of the tube of the oil nozzle that extends radially from the mounting collar.
In order to achieve this objective, it is possible to provide a protruding locating spigot on an arm that forms part of the base of the oil nozzle and extends generally radially from the mounting collar and to drill a second bore in the engine block to receive the locating spigot.
It is convenient to form the second bore of the same diameter as the first bore as this enables the same drilling spindle to be used for both bores.
Advantageously, the spigot on the radially extending arm of the oil nozzle may be formed with two diametrically opposed flats to allow some tolerance in the spacing between the two bores in the block without affecting the orientation of the oil nozzle in the engine block.
In accordance with a second aspect of the invention, there is provided an oil nozzle mounted on an engine block to direct oil towards the underside of a reciprocating piston, the oil nozzle comprising an annular mounting collar having a cylindrical outer surface and a tube projecting generally radially from the mounting collar; and the engine block being formed with a drilled and tapped screw threaded bore that is drilled into the surface of the engine block to intersect an oil gallery in the engine block; and wherein

the engine block additionally is formed with a cylindrical recess that is machined in the surface of the cylinder block surrounding the mouth of the bore to receive and locate the mounting collar of the nozzle; the cylindrical recess and the bore being formed at the same time using a suitably shaped drilling tool so as to ensure on the one hand that the recess and the bore are concentric and on the other hand that the machined sealing surface of the recess is normal to the axis of the bore;
a capscrew is inserted with radial play through the collar into the threaded bore to retain the collar within the recess and to seal the collar against the sealing surface of the recess; the capscrew allowing oil to flow from the oil gallery in the block into the mounting collar of the oil nozzle.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a section through an engine block fitted with a cooling nozzle;
Figure 2 is a schematic plan view from above of a cooling nozzle;
Figure 3 is a partial section through an engine block showing a cooling nozzle mounted in position; and
Figure 4 is a side view of the capscrew used to mount the cooling nozzle in position.
Figure 1 shows a section through one cylinder of an engine block 10 with the piston 12 at the bottom of its stroke. To cool the piston 12, a cooling nozzle 14 sprays oil onto the underside of the piston 12. The cooling nozzle, as shown more clearly in Figure 2, has a base that comprises an annular mounting collar 16 and a radially extending arm 18. A locating spigot 20 with two flats 22, 24 projects from the arm 20. In use, engine oil enters the annular collar 16 and flows through a radial tube 38 to the discharge orifice 40 from which the oil emerges as a jet.
The nozzle 14 is held on the engine block by means of a capscrew 28 that passes through a central hole 26 of the annular collar 16 into a threaded bore 30 that is drilled and tapped in the engine block. The threaded bore 30 extends into an oil gallery 32 or rifle that contains oil pressurised by the engine oil pump.
As can clearly be seen from Figure 1, the space available for the spray nozzle is very restricted and accurate positioning of the nozzle is required if collision is to be avoided with the skirt 34 of the piston 12 and with any part of the crankshaft, the locus of which is represented by the circle 36 in Figure 1.
Conventionally, the entire under surface of the engine block 10 on which the cooling nozzles of the pistons are mounted is milled flat and the position of each nozzle 14 is determined by the position of the capscrew 28 that holds it against the engine block. This requires accuracy not only in the drilling but also in the tapping of the bores 30.
Referring now to Figure 3, in the present invention the collar 16 of the nozzle 14 does not sit on a flat surface but in a cylindrical recess 44 that surrounds the tapped bore 30 that receives the capscrew 28. The cylindrical recess 44 is formed using the same tool as used to drill the bore 30. As is well known, the accuracy with which a bore can be drilled is greater than the accuracy with which one can centre a tapped thread and the position of the cylindrical recess can accordingly be fixed with greater accuracy than the axis of the centre of the capscrew 28. The position of the annular collar is in turn determined by the cylindrical recess and it can therefore be more accurately located. As the same tool is used to drill the bore 30 and to cut the recess 44, the two are automatically concentric and the sealing surface of the recess 44 is automatically normal to the axis of the bore 30.
To fix the orientation of the base of the nozzle 14, a second shallower hole 42 is drilled in the engine block 10, preferably using the same tool, to receive the spigot 20 at the end of the arm 18 connected to the base of the nozzle 14. Because of the flats 22 and 24 on the spigot 20, if the bore 42 has a slightly larger diameter than the spigot 20, some tolerance is afforded in the spacing of the bores 30 and 42 without greatly affecting the angular position of the nozzle 14 relative to the engine block 10.
As the capscrew 28 was conventionally used to locate the base of the nozzle 14, it had to have an outside diameter equal to that of the central hole 26 in the collar 16. Furthermore it had to be machined to provide a passage through which oil could flow from the oil gallery 32 into the collar of the nozzle. By contrast, because in the present invention the capscrew is not used to locate the nozzle and, on the contrary it can be misaligned with the centre of the hole 26, there can and should be a clearance between the stem of the capscrew 28 and the annular collar 16. The capscrew may therefore be as shown in Figure 4 with the section 50 of the stem located in the collar 16 having a reduced diameter to allow for misalignment and to define an annular gap though which oil can flow to the tube 38 and the discharge orifice 40. The stem of the capscrew 50 may also be formed with one or more axially extending surface grooves 52 that are deeper than the thread 54. These grooves 52 may be formed in the blank of the capscrew and as they are deeper than the thread 54 they will not be affected by the male thread. As a result, the capscrew can be formed simply in a single operation and none of its dimensions is critical to the alignment of the cooling nozzle on the engine block.

Claims

A method of mounting an oil nozzle (14) on an engine block (10), the oil nozzle (14) comprising an annular mounting collar (16) having a cylindrical outer surface and a tube (38) projecting generally radially from the mounting collar (16); and
characterized in that the method comprises the steps of :

drilling a bore (30) in the engine block (10) to intersect an oil gallery (32) in the engine block (10);

machining a cylindrical recess (44) in the surface of the cylinder block (10) surrounding the mouth of the bore (30) for receiving and locating the mounting collar (16) of the nozzle (14); the cylindrical recess (44) and the bore (30) being formed at the same time using a suitably shaped drilling tool so as to ensure on the one hand that the recess (44) and the bore (30) are concentric and on the other hand that the machined sealing surface of the recess (44) is normal to the axis of the bore (30);

tapping a thread in the bore (30);

placing the mounting collar (16) of the nozzle (14) in the recess (44);

inserting a capscrew (28) with radial play through the collar (16) into the threaded bore (30) to retain the collar (16) within the recess (44); the capscrew (28) allowing oil to flow from the oil gallery (32) in the block (10) into the mounting collar (16) of the oil nozzle (14); and

sealing the collar (16) against the sealing surface of the recess (44) by means of the capscrew (28).
A method according to claim 1, characterized in that the capscrew (28) is formed by providing a blank having one or more axially extending oil grooves (52) in its surface and cutting a thread (54) in the blank that is less deep than the grooves (52).
A method according to any of the preceding claims, characterized in that a protruding locating spigot (20) is provided on an arm (18) that forms part of the base (16) of the oil nozzle (14) and extends generally radially from the mounting collar (16) and wherein a second bore (42) is drilled in the engine block (10) to receive the locating spigot (20).
A method according to claim 3, characterized in that the second bore (42) is formed of the same diameter as the first bore (30) and is drilled using the same tool as the first bore (30).
An oil nozzle (14) mounted on an engine block (10) to direct oil towards the underside of a reciprocating piston (12); the oil nozzle (14) comprising an annular mounting collar (16) having a cylindrical outer surface and a tube (38) projecting generally radially from the mounting collar (16); and the engine block (10) being formed with a drilled and tapped screw threaded bore (30) that is drilled into the surface of the engine block (10) to intersect an oil gallery (32) in the engine block (10); and
characterized in that :

the engine block (10) additionally is formed with a cylindrical recess (44) that is machined in the surface of the cylinder block (10) surrounding the mouth of the bore (30) to receive and locate the mounting collar (16) of the nozzle (14); the cylindrical recess (44) and the bore (30) being formed at the same time using a suitably shaped drilling tool so as to ensure on the one hand that the recess (44) and the bore (30) are concentric and on the other hand that the machined sealing surface of the recess (44) is normal to the axis of the bore (30);

a capscrew (28) is inserted with radial play through the collar (16) into the threaded bore (30) to retain the collar (16) within the recess (44) and to seal the collar (16) against the sealing surface of the recess (44); the capscrew (28) allowing oil to flow from the oil gallery (32) in the block (10) into the mounting collar (16) of the oil nozzle (14).
A combination according to claim 5, characterized in that the capscrew (28) has a threaded stem (54) with a section (50) of reduced diameter and oil grooves (52) extending axially in the surface of the stem (54) from the reduced diameter section (50) through the thread to the free end of the capscrew (28).
A combination according to claim 5 or 6, characterized in that a protruding locating spigot (20) is provided on an arm (18) that forms part of the base (16) of the oil nozzle (14) and extends generally radially from the mounting collar (16) and wherein a second bore (42) is formed in the engine block (10) to receive the locating spigot (20).
A combination according to claim 7, characterized in that the second bore (42) is formed of
the same diameter as the first bore (30) and is drilled using the same tool as the first bore (30).
A combination according to claims 7 or 8, characterized in that the spigot (20) has a smaller outer diameter than the second bore (42) and has two flats (22, 24) so as to increase the tolerance of the distance between the bores (30, 42) drilled in the engine block (10).